The present invention relates to novel devices for illuminating a target with a coherent beam of radiant energy, typically, although not necessarily, operating in the covert, near infrared portion of the electromagnetic spectrum, and capable of functioning simultaneously as both a source of illumination and a pointing device.
In the interest of brevity and clarity, the principles of the present invention will be developed in large part with reference to target illumination and aiming. This is not intended to limit the scope of the invention as defined in the appended claims as there are many other applications of laser illuminators employing these principles such as medical technology or surveying.
The invention disclosed here is an improvement on the type of night vision system disclosed in U.S. Pat. No. 5,056,097 entitled TARGET ILLUMINATORS AND SYSTEMS EMPLOYING SAME (xe2x80x9cthe ""097 patentxe2x80x9d) which is hereby incorporated by reference into this specification. The ""097 patent disclosed a night vision target illumination device that uses a laser to provide illumination. The illumination device is an xe2x80x9cinfrared laser xe2x80x9d system. In other words, the laser is used to illuminate a target area that is invisible to the naked eye and can only be seen by viewing the target area through an image intensifier or other infrared sensing device.
An important advantage of a laser-based device over earlier designs (i.e., LED-based devices) is that the laser-based device can illuminate a target area at a much greater distance. Earlier LED-based devices were limited in their ability to produce adequate visual images at ranges approaching 500 feet and beyond. Laser-based devices are limited only by their power output.
The laser-based system can be built with a zoom function that allows adjustment of the size of the illuminated target area. Obviously, enlarging the target area gives the user a wider field of view. But, the laser can also be focused to a point (i.e., xe2x80x9ctarget pointxe2x80x9d) and therefore function as an invisible targeting device (i.e., xe2x80x9cgun sightxe2x80x9d).
The use of visible lasers as gun sights for weapons targeting is, of course, well known and has been used by the military, police SWAT teams, and the like. They create a targeting point or spot (e.g., a red xe2x80x9cdotxe2x80x9d) that is visible to the naked eye. In the case of the invisible laser, the target point can be seen only through special infrared or night vision imaging devices.
If the invisible laser is focused to a small target point in the dark, then the user (who views the area illuminated by the laser through the night vision imaging devices) cannot see anything in the dark but the target point itself. Consequently, heretofore invented has been a dual laser system that uses one laser for the targeting point function and a second laser to create a larger, viewable field around the target point. By taking advantage of the features of the dual laser system, the user can see where the target point should be moved as necessary.
The present invention is an improvement over the dual laser system described above.
The invention disclosed herein is a dual function, single laser device. Rather than using two laser emitters, the device uses a single laser in combination with a unique arrangement of lenses to produce both a xe2x80x9ctargetingxe2x80x9d function (pinpoint dot) and a variable sized xe2x80x9cfield of illuminationxe2x80x9d function as described above. This is accomplished by placing a first lens downstream of a laser diode for focusing the laser""s beam along a converging path. A second lens arrangement is positioned within the envelope of the beam path and fans a portion of the beam outwardly along a diverging path. The first lens is used to focus a portion of the laser""s beam to a target point for sighting purposes. The second lens arrangement causes a central portion of the beam to spread outwardly and create an illumination field around the target point.
The second lens arrangement can be made in different ways. One type of lens arrangement uses a pair of sub-aperture lenses positioned downstream of the first lens, but still within the xe2x80x9cfootprintxe2x80x9d of the laser beam after it passes through the first lens. The specific details of this particular embodiment, and others, are described below.
The invention provides many advantages over existing laser-based devices. By using lenses to create both the targeting and viewing functions, one laser emitter can do the job of two. An advantage of using a single laser emitter is that a laser targeting device can be simplified and made at lower carrying weight and reduced cost relative to prior designs. When two laser emitters are used, each requires its own electronics and power. Therefore, reducing the number of emitters from two to one significantly simplifies the design, and reduces the cost of an invisible targeting device.